Method for manufacturing a waveguide including a semi-conducting junction

ABSTRACT

The invention relates to a method for manufacturing a waveguide ( 40 ) including a semiconducting junction ( 23 ). The method comprises the following steps: providing a support ( 10 ) comprising a semiconducting layer ( 20 ) having a first part ( 21 ) of a first conductivity type ; protecting the first part ; selectively implanting a second conductivity-type dopants in a second part ( 22 ) of the semiconducting layer ( 20 ) adjacent to the first part ( 21, 221 ). The concentration of second conductivity-type dopants in the second part ( 22, 222 ) is greater than the one of first conductivity-type dopants in the first part ( 21, 221 ). The method further comprises the steps of: diffusing second conductivity-type dopants in the first part ( 21, 221 ) to form a semiconducting junction ( 23, 223 ) in the first part ( 21, 221 ), and partially etching the semiconducting layer ( 20, 200 ) to form the waveguide ( 40, 240 ) in the first part ( 21, 221 ), the protection of the first part ( 21, 221 ) being used so that the semiconducting junction ( 23, 223 ) is included in the waveguide ( 40, 240 ).

TECHNICAL FIELD

The invention relates to the fields of microelectronics andoptoelectronics and more particularly relates to the methods formanufacturing semiconducting structures for integrated optoelectronics,such as optical modulators.

STATE OF PRIOR ART

The optical modulators, such as the Mach-Zehnder or resonant ring-typemodulators, usually integrate a waveguide the optical properties ofwhich can be modulated.

Such a waveguide the optical properties of which can be modulated isusually provided by a semiconducting waveguide into which asemiconducting junction has previously being included. Indeed, theoptical properties of such a waveguide, such as the effective index, canbe easily modulated by adequately polarizing the semiconductingjunction.

A conventional method for manufacturing such a waveguide consists inimplementing the following steps:

-   -   providing a support including a semiconducting layer, at least        one first part of the layer having a first conductivity type,    -   selectively implanting dopants of a second conductivity type        opposite to the first type in a second part of the        semiconducting layer adjacent to the first part so as to form a        semiconducting junction between both parts,    -   partially etching the layer so as to form the waveguide, the        etching being made so that the semiconducting junction is        included in the waveguide.

These two latter steps both necessarily involve a procedure of maskingthe semiconducting layer, in order to position the implantation area ofthe first conductivity type and the waveguide during etching. But thejunction must be positioned in proximity to the centre of the waveguide,which prevents any reuse of the masks used during the implantation toperform the etching. Thus, the masking procedure during the step ofetching is necessarily made with an alignment of the etching mask withrespect to the previously implanted junction.

This alignment, due to the sizing of the waveguide and because thejunction must be accurately positioned with respect to the centre of thewaveguide, is relatively complex to set up and drastically increases themanufacturing cost of such a waveguide.

Document US20130058606 A1 teaches that it is possible, by implanting thejunction after forming the waveguide, to use the masking used during thestep of etching in order to define the location of the junction.

The method described in this document thus consists in implementing thefollowing main steps:

-   -   providing a support including a semiconducting layer, at least        one first part of the layer having a first conductivity type,    -   partially etching the layer so as to form the waveguide in the        first part of the layer,    -   selectively implanting a second part of the remaining        semiconducting layer after etching, the waveguide being        protected during implanting by the mask previously used during        etching so that the second implanted part is adjacent to the        guide;    -   thermal treatment to activate the dopants, said treatment        leading to a low diffusion of the junction inside the waveguide.

Thus, the formed junction is perfectly positioned with respect to thewaveguide without requiring an accurate alignment of the mask.Manufacturing a waveguide with such a method has therefore a reducedcost with an increased accuracy of the positioning of the junction withrespect to the waveguide.

Nevertheless, if such a method enables a good control of the positioningof the junction with respect to the waveguide without drasticallyincreasing the manufacturing cost, the junction inevitably lies inproximity to a wall of the waveguide and is therefore remote from thecentre of the waveguide. But, to achieve an optimized operation of thewaveguide and a maximum modulation of the optical property at the centreof the waveguide with limited optical losses, it is necessary for thejunction to be positioned in proximity to the centre of the waveguide.It is moreover to be noted that diffusing the dopants during the step ofactivating does not allow a vertical junction to be obtained. Indeed,since the diffusion occurs from the lower edge of the waveguide, thejunction resulting from this diffusion remains centred with respect tothe same lower edge.

DISCLOSURE OF THE INVENTION

The aim of the invention is to resolve this drawback and the objectthereof is to make possible to provide a waveguide at least one opticalproperty of which can be modified, without requiring, to provide thewaveguide with an accurate positioning of the junction in proximity tothe centre of the waveguide, any significant additional cost related tothe alignment of the mask.

The aim of the invention is further to provide such a waveguide with anorientation of the junction substantially transverse with respect to theplane of the support of said waveguide, this corresponding, in aconventional configuration, to a vertical orientation of the junction.

To this end, the invention relates to a method for manufacturing awaveguide including a semiconducting junction, said method comprisingthe following steps:

-   -   providing a support comprising a semiconducting layer having at        least one first part of a first conductivity type comprising a        concentration of first conductivity-type dopants,    -   protecting the first part of the semiconducting layer,    -   selectively implanting dopants of a second conductivity type        opposite to the first conductivity type in a second part of the        semiconducting layer, the implantation selectivity being        achieved by means of the protection of the first part so that        the second part is adjacent to the first part, the implantation        being made so that the concentration of second conductivity-type        dopants in the second part is greater than the one of first        conductivity-type dopants in the first part,    -   diffusing second conductivity-type dopants in the first part to        form a semiconducting junction in the first part,    -   partially etching the semiconducting layer to form the waveguide        in the first part, the protection of the first part being used        during this etching to bound a first side wall of the waveguide        at the interface between the first and the second parts so that        the semiconducting junction is included in the waveguide.

With such a method, positioning the junction with respect to the firstside wall of the waveguide is determined by the diffusion length of thesecond conductivity-type dopants in the first part. Thus, with anadapted diffusion of the second conductivity-type dopants, it ispossible to achieve an optimum positioning of the junction with respectto the first wall and therefore to the centre of the waveguide. Such amethod then enables the junction to be positioned in proximity to thecentre of the waveguide. Moreover, since the diffusion occurs from thevertical interface between the first and the second part, the finalorientation of the junction in the waveguide is also vertical, that istransverse with respect to the support of the waveguide.

It is also to be noted that the optimum positioning and orientation ofthe junction with respect to the centre of the waveguide does not leadto any significant additional cost as is the case for the prior artmethods since the alignment of the mask for etching is mainly achievedby reusing the protection used during implanting.

It is to be noted that, of course, if the semiconducting layer has afirst part of a first conductivity type, this characteristics does notpredict the conductivity type of the remainder of the semiconductinglayer at all. Thus, it can be contemplated within the scope of theinvention that the remainder of the semiconducting layer is totally orpartially of the first conductivity type or even that the remainder ofthe semiconducting layer is of the second conductivity type or of theintrinsic type.

The manufacturing method being a method for manufacturing a waveguide ofa width W, the concentration of second conductivity-type dopantsimplanted during the implanting step can be adapted so that during thestep of diffusing the second conductivity-type dopants in the firstpart, diffusion occurs from the interface between the first and thesecond parts over a distance between 10 and 70% of the width W,preferentially between 30 and 50% of the width W.

With such an adaptation of the concentration of the secondconductivity-type dopants, a simple annealing during the step ofdiffusion enables an adequate placing of the junction to be provided forthe inclusion thereof in the waveguide. Indeed, with such aconcentration, the annealing conditions, if they are sufficient to allowa maximum diffusion of the dopants, do not need to be perfectlycontrolled. It is the concentration of dopants in the first and thesecond parts of the semiconducting layer which defines the distance ofdiffusion.

The ratio of the concentration of second conductivity-type dopantsimplanted in the second part to the one of the first conductivity-typedopants in the first part may be between 2 and 30 and is preferentiallybetween 4 and 15.

With an implantation of second conductivity-type dopants during the stepof implanting, it is possible to provide an optimum placing of thesemiconducting junction through a step of diffusing consisting in asimple annealing enabling a maximum diffusion of the secondconductivity-type dopants to be provided.

Upon providing the support, the area of the layer which is intended toform the second part can also be of the first conductivity type andinclude a concentration of first conductivity-type dopants substantiallyidentical to the one of the first part.

During the step of protecting the first part, a first mask can bedeposited which protects the area of the first part intended to form thewaveguide during the steps of implanting and etching and a second maskcan also be deposited which protects the remainder of the first partduring implanting, the method including, prior to the step of etching, astep of removing the second mask.

The use of two protecting elements, a first mask protecting the area ofthe first part intended to form the waveguide and a second maskprotecting the remainder of the first part, enables a simplified use ofthe protection during the step of partial etching. Indeed, a selectiveremoval of the second protecting element enables an adequate protectionto be achieved to protect the area intended to form the waveguide duringthe step of partial etching.

The support can be a semiconductor-on-insulator-type support, thesemiconducting layer being the semiconducting layer on insulator of thesupport.

Such a support is particularly adapted to provide a good qualitywaveguide, the insulating layer contributing to confining theelectromagnetic wave passing through the waveguide.

The semiconducting layer can be a silicon layer.

Such a layer is particularly adapted for obtaining a waveguide havinggood optical characteristics for the electromagnetic waves in theinfrared range.

The ones among the first and second conductivity-type dopants can beselected from the group comprising boron, aluminium and indium, whereasthe others among the first and second conductivity-type dopants can beselected from the group including phosphorus, arsenic and antimony, thefirst and second conductivity-type dopants being preferentially boronfor the ones and phosphorus for the others.

The step of diffusing can consist in applying a thermal annealing to thesupport adapted to achieve a diffusing distance of the secondconductivity-type dopants in the first part which is maximum.

Thus, the diffusing distance is perfectly defined since this distance isdetermined by the concentration of the implanted secondconductivity-type dopants.

The invention further relates to a method for manufacturing anoptoelectronic component having a waveguide including a semiconductingjunction, the manufacturing method comprising the steps formanufacturing a waveguide according to the invention.

Such a method makes it possible to enjoy advantages related to themethod for manufacturing a waveguide according to the invention.

The optoelectronic component can be an optical modulator such as aMach-Zehnder-type or resonant ring-type modulator.

Such an optical modulator particularly enjoys the possibility given bythe method for manufacturing a waveguide according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood upon reading thedescription of exemplary embodiments, given by way of purely indicatingand in no way limiting purposes, with reference to the appended drawingsin which:

FIGS. 1A to 1D illustrate the steps for manufacturing a waveguideaccording to the principle of the invention, said waveguide including asemiconducting junction,

FIG. 2 is a graph showing the displacement of the junction as a functionof the concentration of implanted dopants during the step of implanting,

FIGS. 3A to 3D respectively and graphically illustrate the variation inthe concentration of the first and second conductivity-types dopantsalong a transverse cross-section of four respective waveguides obtainedby implanting second conductivity-type dopants with differentconcentrations,

FIGS. 4A to 4N illustrate the main steps for manufacturing asemiconducting component, such as a modulator, including a waveguideaccording to the invention.

Identical, similar or equivalent parts of the different figures bear thesame reference numerals so as to facilitate switching from one figure tothe other.

The different parts represented in the figures are not necessarily drawnto a uniform scale, in order to make the figures more understandable.

The different possibilities (alternatives and embodiments) must beunderstood as being not mutually exclusive and can be combined to eachother.

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

FIGS. 1A to 1D illustrate the main steps for manufacturing a waveguide40 according to the invention having optical properties which can bemodulated and which is able to be comprised in a component such as aMach-Zehnder-type or ring-type optical modulator.

Thus, according to the principle of the invention illustratedschematically and in a transverse cross-section in FIG. 1D, a component1 having such a waveguide 40 includes a support 10, such as here, asilicon substrate on which an insulator layer is disposed according tothe silicon-on-insulator principle, more commonly known as the acronymSOI, only the insulating layer being represented.

Said support 10 comprises a semiconducting layer 20 having a first part21 mainly of a first conductivity type and a second part 22 of a secondconductivity type adjacent to the first part 21, the first part having,in proximity to the second part 22, a portion of the second conductivitytype so that a semiconducting junction 23 is formed in the first part 21in proximity to the second part 22.

For the purpose of clarity and by means of illustration, in thecontinuation of the description of the invention, the first conductivitytype is defined as the conductivity type for which the majority carriersare holes, the latter being referred to by convenience as “P-type”,whereas the second conductivity type is defined as the conductivity typefor which the majority carriers are electrons, the latter being referredto by convenience as “N-type”. Thus, a portion having the first andsecond conductivity types is respectively referred to as P-doped andN-doped. Of course, this choice does not limit whatsoever the scope ofthe invention since the first and second conductivity types can bereversed without departing from the scope of the invention.

The semiconducting layer 20 comprises, as illustrated in FIG. 1D, thewaveguide 40 provided therein so that the junction 23 is included in thewaveguide 40. The waveguide is formed by an extra thickness of thesemiconducting layer 20 which protrudes from the remainder of thesemiconducting layer 20 over a height h which can be between 100 and 500nm. The width W of the waveguide can be between 100 and 500 nm. Thewaveguide extends along a direction which is referred to as longitudinalas opposed to its lateral direction along which the cross-sectionillustrated in FIG. 1D is made. This longitudinal direction can be, as afunction of the component fitted with a waveguide 40, linear,curvilinear, and even ring-shaped.

The waveguide 40 comprises a first portion 41 of the first P-doped part21 and a second portion 42 of the first part 21 which is the N-dopedportion. The interface between the first and the second portions 41, 42of the waveguide then forms the junction 23. The first and the secondportions 41, 42 and the junction 23 are longitudinal and all threeextend along the longitudinal direction of the waveguide 40.

Along the transverse direction, the junction 23 is positioned at adistance d from the centre of the waveguide 40. The distance d isbetween 0 and 45% of the width W of the waveguide, that is 0 and 90% ofthe half-width W/2.

The method for manufacturing such a waveguide 40 comprises the followingsteps:

-   -   providing, as illustrated in FIG. 1A, the support 10 comprising        the semiconducting layer 20 comprising at least one first        P-doped part 21 with a first concentration of P-type dopants,    -   protecting the first part 21 of the semiconducting layer 20,    -   selectively implanting, as illustrated in FIG. 1B, N-type        dopants in a second part 22 of the semiconducting layer 20, the        implantation selectively being achieved by means of protecting        the first part 21 so that the second part 22 is adjacent to the        first part 21, the implantation being made so that the        concentration of N-type dopants is greater than the one of        P-type dopants in the first part 21,    -   diffusing, as illustrated in FIG. 1C, N-type dopants in the        first part 21 to form a semiconducting junction 23 in the first        part 21,    -   partially etching, as illustrated in FIG. 1D, the semiconducting        layer 20 to form the waveguide 40 in the first part 21, the        protection of the first part 21 being used during this etching        to bound a first side wall of the waveguide 40 at the interface        between the first and second parts 21, 22 so that the        semiconducting junction 23 is included in the waveguide.

In an exemplary practical embodiment of the invention, the support 10 isa silicon-on-insulator-type support, the silicon layer of such a supportforming the semiconducting layer 20. The step of providing the support10 according to this example includes a first sub-step of providing asilicon-on-insulator-type support with the surface silicon layer beingnon-intentionally doped.

According to this same practical embodiment, forming the first part 21of the P-doped semiconducting layer 20 is made by a sub-step ofimplanting the semiconducting layer 20 with P-type dopants. Thesedopants can be boron. The implantation is made by ion implantation witha dopant dose of 1×10¹³ cm⁻² and an implantation energy of 46 KeV. Thisway, the whole semiconducting layer 20, including its first part 21, isP-doped.

The step of protecting the first part 21 can be performed by means oftwo different masks 31, 32, a first mask 31 protecting the area of thefirst part 21 which will form, after etching, the waveguide 40, thisfirst mask 31 being, in FIG. 1B, a hard mask, and a second mask 32, ofthe resin type or any type of material having an etching selectivitywith respect to the mask 31 and the semiconducting layer 20, protectingthe remainder of the first part 21 which is not protected by the firstmask 31. The first mask 31 is sized, for the practical exemplaryembodiment, to form a waveguide 40 with a width of 320 nm.

It can be seen in FIG. 1B that placing the second mask 32 with respectto the first mask 31 does not require an accurate alignment operationsince the overlapping area of the second mask 32 on the first mask 31enables a possible misalignment of the second mask 32 with respect tothe first mask 31 to be counterbalanced.

The first and second masks 31, 32 enable the first part 21 of thesemiconducting layer 20 to be protected during the step of implantingthe second part 22.

In the exemplary practical embodiment, the implanted secondconductivity-type dopants are phosphorus. Implanting is made by ionimplantation with a dopant dose strictly greater than 1×10¹³ cm⁻², andequal to or lower than 1×10¹⁵ cm⁻², and an implantation energy of 130KeV. This way, implanting the second part 22 is made with aconcentration of dopants greater than the one of the first part 21 sincea concentration of 7×10¹⁷ cm⁻³ is obtained in the first part 21, apartfrom the waveguide, and of 7×10¹⁷ to 1×10¹⁹ cm⁻³, in the second part 22.

Such a difference in the concentration of dopants between the first andthe second parts 21, 22 enables, with the annealing conditions of thestep of diffusing, the distance D along which the P-type dopants diffusein the first part 21 to be defined. Such a distance can be referred toas, to simplify, a diffusion distance of the junction.

FIG. 2 then illustrates the diffusion distance D of the junction 23 as afunction of the dose C implanted with N-type dopants within the scope ofthe exemplary practical embodiment. This graph shows that for areference value in which the dose of dopants in the second part 22 isidentical to the one of the first area, that is equal to 1×10¹³ cm⁻²,the N-type dopants hardly diffuse, or even do not diffuse at all. Thediffusion distance of the junction for this dose is therefore 0 nm.

When the implanting dose of N-type dopants becomes greater than the oneof P-type dopants in the first part 21, the annealing enables adiffusion to be achieved. This diffusion is all the more significantthat the ratio of the dose of N-type dopants to the one of P-typedopants increases. This diffusion varies in a substantially logarithmicway with this ratio, and therefore with the implanted dose ofphosphorous, as illustrated in FIG. 2.

It is this variation which is illustrated in FIGS. 3A to 3D. Indeed,FIGS. 3A to 3D respectively represent the variation in concentration ofdopants C′ along a transverse cross-section for a waveguide afterdiffusion for a respective implantation of 1×10¹³ cm⁻², 1.2×10¹⁴ cm⁻²,2.3×10¹⁴ cm⁻² and 1×10¹⁵ cm⁻² of phosphorus in the second part of thesemiconducting layer, and a dose of 1×10¹³ cm⁻² of boron in the firstpart 21. The junction 23 is thus respectively positioned at 720 nm, 625nm, 595 nm, and 550 nm. Knowing that the walls of the waveguide arerespectively positioned at 720 and 400 nm, these positions correspond toa respective positioning with respect to the centre of the waveguide of100%, 46%, 21%, and −6% of the half-width W/2 of the waveguide 40according to the particular exemplary embodiment. It is thus possiblewith a simple variation in the dose of dopants implanted in the secondpart 22 to define the positioning of the junction with respect to thecentre of the waveguide.

With the configuration described in the exemplary embodiment, apositioning d of the junction with respect to the centre of thewaveguide 40 of 10% to 20% of the width of the waveguide, that is 20% to40% of the half-width W/2, can be considered as optimum to enable aproper modulation of the optical characteristics of the waveguide 40while limiting the optical losses. Such a positioning can therefore beachieved, as shown in FIG. 3C and 3B, for a phosphorus dose between1.2×10¹⁴ cm⁻² and 2.3×10¹⁴ cm⁻² and a boron dose of 1×10¹³ cm⁻². Thiscorresponds to a factor in the order of 10 to 20 with respect to theboron dose which has been implanted in the first part 21 of thesemiconducting layer 20, which results in a ratio of concentration ofdopants in the first and the second parts 21, 22 before diffusion of 4to 6. It will be noted that a positioning d of the junction with respectto the centre of the waveguide 40 of 20% of the half-width of thewaveguide is to be preferred, and therefore a factor of 10 with respectto the boron dose is advantageous for the phosphorus dose. Such a doseratio corresponds to a ratio of the concentration of dopants in thefirst and the second parts 21, 22 before diffusion of 4.

After implanting the second part 22 of the semiconducting layer 20, thestep of diffusing can be made through annealing the support10/semiconducting layer 20 assembly at 1050° C. during 10s. Such anannealing is sufficient for the diffusion distance of the N-type dopantsin the first part 21 to be maximum. A maximum diffusion of the junction23 in the first part 21 of the semiconducting layer 20 is then alsoachieved, the junction 23 being positioned in the first part 21 of thesemiconducting layer 20.

The step of partial etching, such as illustrated in FIG. 1D, includesthe following sub-steps:

-   -   removing the second mask 32 so as to leave protected only the        area of the first part 21 lying under the first mask 31 and        which is intended to be included in the waveguide 40, the        junction 23 being in the area protected by the first mask 31,    -   etching the non-protected areas of the semiconducting layer 20        over a height h so as to form the waveguide 40,    -   removing the first mask 31.

The sub-step of etching can also be a wet etching, such as by etching bymeans of an acid, or a dry etching, such as by reactive ion etching.Moreover, since the area of the semiconducting layer intended to formthe waveguide is protected by the first mask 31, the protection of thefirst part is then used during etching in order especially to bound afirst side wall of the waveguide 40 at the interface between the firstand the second parts 21, 22.

Thus, since the junction 23 is included in the area of thesemiconducting layer 20 protected by the first mask 31, it is includedin the waveguide 40. Furthermore, the location of the walls of thewaveguide is defined by the first mask 31 with one of those whichcorresponds to the interface between the first and the second parts 21,22. As a result, the positioning of the junction 23 defined by diffusingN-type dopants from the interface between the first and the second parts21, 22, is also defined with respect to the wall of the waveguide 40corresponding to the same interface.

The positioning of the junction 23 in the waveguide 40 is thereforeperfectly defined without having required a demanding step of aligningthe mask.

Such a method can be implemented for manufacturing an optoelectroniccomponent such as an optical modulator either of the Mach-Zehnder-typeor of the resonant ring-type. FIGS. 4A to 4N actually illustrate theintegration of a method for manufacturing a waveguide according to theinvention as part of the manufacture of an optoelectronic component 1including such a waveguide. This component includes an optical modulatorsuch as a Mach-Zehnder or resonant ring-type optical modulator.

Said component 1 includes, as illustrated in FIG. 4N:

-   -   a coupling network 2, such as a grating coupler, adapted to        receive an electromagnetic radiation at a given wavelength,    -   a first waveguide 3,    -   a second waveguide 4, said second waveguide 4 being a waveguide        according to the invention and thus includes a junction 223,        said second waveguide 4 further comprising contacts 204, 205 to        enable a polarization of its junction 223 and a resistive        element 206 forming a heating system to make it possible to        counterbalance the temperature variations which could lead to a        shift in its optical response,    -   a photodiode 5 adapted to receive a radiation.

It is to be noted that if FIGS. 4A to 4N illustrate transversecross-section views, these different elements of the componentillustrated in FIG. 4N are of course in three dimensions and thereforehave connections to each other which are not present in thecross-section plane.

Thus, in the case where the optical modulator is of theMach-Zehnder-type, the coupling network 2 is optically connected to thefirst and the second waveguides 3, 4 so that the latter each form one ofthe branches of a Mach-Zehnder-type optical modulator, the output of thethus formed modulator being itself optically connected to the photodiode5.

In the case where the modulator is of the resonant ring-type, thecoupling network 2 is optically connected to the first waveguide 3, thelatter being optically coupled to the second waveguide 4 which forms aresonant ring. The output of the first waveguide, therefore the one ofthe optical modulator, is optically connected to the photodiode 5.

A method for manufacturing such a component includes the followingsteps:

-   -   providing an SOI-type semiconducting support 100, the        semiconducting layer 200 including a silicon dioxide shield at        its surface,    -   depositing a mask 301, said mask including an aperture for        forming a first P-doped area 201 in the semiconducting layer        200,    -   implanting P-type dopants in the area 201 of the non-protected        semiconducting layer, such as illustrated in FIG. 4A,    -   removing the mask 301 and depositing another mask 302, said        other mask 302 including an aperture for forming a second        N-doped area 202,    -   implanting N-type dopants in the area 202 of the semiconducting        layer 200 not protected by the mask 302, as illustrated in FIG.        4B,    -   removing the mask 302 and depositing another mask 303, so as to        enable the deposit on an area 203 of the semiconducting layer        200 comprised between the previously implanted areas 201, 202,        said area 203 comprising a first part 221 of the semiconducting        layer 200,    -   implanting P-type dopants in the area 203 of the semiconducting        layer not protected by the mask 302, said area 203 including the        first part 221 of the semiconducting layer 200, such as        illustrated in FIG. 4C,    -   removing the mask 303 and depositing the layer 304 able to form        a first hard mask, such as illustrated in FIG. 4D,    -   depositing a second mask 332 on the layer able to form a first        hard mask 331, this second mask 332 including apertures in order        to etch the layer 304 to form the first mask 331, as illustrated        in FIG. 4E,    -   selectively etching the layer 304 able to form the first mask        331 through the second mask 332 so as to transfer the apertures        of the second mask 332 in said layer 304 and thus form the first        mask 331,    -   adding an additional portion of the material forming the second        mask 332 so as to complete the second mask 332, this addition        being made so as to protect the first part 221 of the        semiconducting layer 200 and so as to leave free a second part        222 of the semiconducting layer 200, as illustrated in FIG. 4F,        such a step thus consists in protecting the first part 221 of        the semiconducting layer 200,    -   selectively implanting N-type dopants in the second part 222 of        the semiconducting layer 200, the implantation selectivity being        achieved by means of the first and the second masks 331, 332,        the implantation being made so that the concentration of N-type        dopants in the second part 222 is greater than the one of P-type        dopants in the first part 221, as illustrated in FIG. 4G,    -   diffusing the N-type dopants in the first part 221 to form a        semiconducting junction 223 in the first part 221, as        illustrated in FIG. 4H,    -   removing the second mask 332,    -   partially etching the semiconducting layer 200 over a height h        through the first mask 331 in order to transfer the apertures of        the first mask 331 on the semiconducting layer 200, said        selective etching enabling the formation of the coupling network        2, the first waveguide 3 and the functional part 240 of the        second waveguide 4, the latter being formed in the first part        221, the first mask 331 being used to bound a first side wall of        the waveguide 4 at the interface between the first and the        second parts 221, 222 so that the semiconducting junction 223 is        included in the waveguide 4,    -   depositing an insulator layer 400, as illustrated in FIG. 4I,    -   partially etching the insulator layer 400 and the semiconducting        layer 220 at an area of the semiconducting layer adjacent to the        functional part 240 of the second waveguide 4 and which is        opposite the coupling network 2, as illustrated by FIG. 4J,    -   depositing germanium in the space freed during the partial        etching so as to form a portion 250 of germanium, as illustrated        in FIG. 4K,    -   implanting P-type and N-type dopants respectively in the first        and the second areas 251, 252 of the deposited portion of        germanium 250, as illustrated in FIG. 4L,    -   diffusing dopants in the portion of germanium 250 so as to form        a semiconducting junction and obtain the photodiode 5,    -   depositing an electrical contact 204, 205 on each of the        adjacent areas 201, 202 of the waveguide 240 so as to enable a        polarization of the junction 223 included in the waveguide by        means of these two electrical contacts 204, 205,    -   depositing an insulator layer,    -   depositing a resistive element 206 overhanging the waveguide,        said resistive element 205 being arranged to transmit heat to        the waveguide when it carries a current so as to make it        possible to counterbalance the thermal variations which could        lead to a shift in the optical response of the waveguide, as        illustrated in FIG. 4M,    -   selectively etching the insulator layer 400 so as to form        passages for vertical interconnections in order to connect the        electrical contacts 204, 205 of the adjacent areas 201, 202 of        the waveguide, the resistive element and both poles of the        germanium photodiode,    -   filling the passages formed in the insulator layer 400 so as to        constitute vertical interconnections 207 to connect the adjacent        areas 201, 202 of the waveguide, the resistive element 206 and        both poles of the germanium photodiode 5,    -   forming surface contacts 208 of the vertical interconnections        207, as illustrated in FIG. 4N.

A component 1 such as obtained by such a method, given by way ofexemplary integration of the waveguide according to the invention, makesit possible to receive an electromagnetic wave on the coupling network2, to make this electromagnetic wave pass through both waveguides 3, 4with the possibility of modulating it by means of an adequatepolarization of the second waveguide 4 and of measuring the thusmodulated wave by means of the germanium photodiode 5. This shows that amethod for manufacturing a waveguide 4 according to the invention can beeasily integrated to a method for manufacturing a more complexoptoelectronic component such as an optical modulator.

If according to the above-described embodiment, the support can be anSOI-type support with the semiconducting layer which is anintrinsic-type silicon-on-insulator layer, the support and thesemiconducting layer it includes can be of another type withoutdeparting from the scope of the invention. Thus, the support can easilyinclude a semiconducting layer of another type, such as germanium,silicon carbide or indium phosphorus. Of course, the first and secondconductivity-type dopants are to be adapted as a function of thesemiconducting material constituting the semiconducting layer. Sincesuch adaptations are known from those skilled in the art, the latter isable to transpose the method according to the invention to thesesemiconducting materials by means of simple routing tests.

Thus, taking only the example of silicon, the first and secondconductivity-type dopants can be selected in the group including boron,aluminium and indium whereas others among the first and secondconductivity-type dopants are selected from the group includingphosphorus, arsenic and antimony. These alternatives to boron andphosphorus are usual and those skilled in the art are perfectly able,from the teaching of this document and from their general knowledge, toadapt the method according to the invention to these different dopants.

1. A method for manufacturing a waveguide including a semiconducting junction, the method comprising: providing a support comprising a semiconducting layer having at least one first part of a first conductivity type comprising a concentration of first conductivity-type dopants, protecting the first part of the semiconducting layer by providing a protection of the first part, selectively implanting dopants of a second conductivity type opposite to the first conductivity type in a second part of the semiconducting layer, the implantation selectivity being achieved by means of the protection of the first part so that the second part is adjacent to the first part, the implantation being made so that the concentration of second conductivity-type dopants in the second part is greater than the one of the first conductivity-type dopants in the first part, diffusing the dopants of the second conductivity type in the first part to form a semiconducting junction in the first part, after the steps of implanting and diffusing have been performed, partially etching the semiconducting layer to form the waveguide in the first part, the protection of the first part being used during this etching to bound the first side wall of the waveguide at the interface between the first and the second parts so that the semiconducting junction is included in the waveguide.
 2. The manufacturing method according to claim 1 of a waveguide of a width W, wherein the concentration of the dopants of the second conductivity type implanted during the implanting step is adapted so that during diffusing the dopants of the second conductivity type in the first part, diffusion occurs from the interface between the first and the second parts over a distance between 10 and 70% of the width W.
 3. The manufacturing method according to claim 2, wherein the ratio of the concentration of the dopants of the second conductivity type dopants implanted in the second part to the dopants of the first conductivity type dopants in the first part is between 2 and
 30. 4. The manufacturing method according to claim 1, wherein during providing the support the area of the layer which is intended to form the second part is also of the first conductivity type and includes a concentration of the dopants of the first conductivity type substantially identical to the one of the first part.
 5. The manufacturing method according to claim 1, wherein during the protecting the first part, a first mask is deposited which protects the area of the first part intended to form the waveguide during the steps of implanting and etching and a second mask is also deposited which protects the remainder of the first part during implanting, the manufacturing method comprising prior to the etching a removing the second mask.
 6. The manufacturing method according to claim 1, wherein the support is a semiconductor-on-insulator-type support, the semiconducting layer being the semiconductor layer on insulator of the support.
 7. The manufacturing method according to claim 1, wherein the semiconducting layer is a silicon layer.
 8. The manufacturing method according to claim 7, wherein the ones among the first and second conductivity-type dopants are selected from the group comprising boron, aluminium and indium whereas the others among the first and second conductivity-type dopants are selected from the group including phosphorus, arsenic and antimony.
 9. The manufacturing method according to claim 8, wherein the ones among the first and second conductivity-type dopants is boron, whereas the others among the first and second conductivity-type dopants are phosphorus.
 10. A method for manufacturing an optoelectronic component having a waveguide including a semiconducting junction, the manufacturing method comprising the steps of manufacturing a waveguide according to claim
 1. 11. The manufacturing method according to claim 10, wherein the optoelectronic component includes an optical modulator such as a Mach-Zehnder-type or resonant ring-type modulator. 